The invention pertains generally to organic synthesis and in particular to a controlled method of partially dehydrating a polyol to form an unsaturated alcohol.
Nitrate esters of polyols are used extensively as explosives and as energetic plasticizers for nitrocellulose in propellants. The most commonly used nitrate ester is nitroglycerin, but it has a number of problems. The nitrate ester of 1,2,4-butanetriol has a lower volatility and sensitivity, and is a better plasticizer. It is, unfortunately, much more expensive than nitroglycerin.
It is known that this triol can be easily and cheaply prepared from 3-buten-1-ol, but the unsaturated alcohol is difficult to prepare. Every known method for preparing this alcohol has disadvantages which increase the cost of the final product. A laboratory procedure, reported in J. A. Gallaghan et al, Technical Report 19, Naval Powder Factory, Indian Head, Md. (1948), converts allyl chloride by means of a Barber modification of a Grignard reaction. The yields from this method are high (up to 65%), but attempts at scaling-up this method to production have been unsuccessful.
Attempts at dehydrating butanediol to 3-buten-1-ol have had many problems. Most reactions proceed until the diol has been completely dehydrated to butadiene. The dehydrations which are controllable produce numerous side reactions, causing the product yield to be low. Usually the dehydrations proceed in the gas phase which greatly increases the equipment and energy costs and presents problems in maintaining a uniform temperature throughout the reactor. Many of the catalysts have a short life, are expensive, and are expensive to regenerate.